1. Field of Invention
The present invention relates to a driver circuit. More particularly, the present invention relates to a driver circuit used to turn on the backlight module of a liquid crystal display (LCD).
2. Description of Related Art
FIG. 1 shows the framework of an LCD 100. The LCD 100 comprises a pixel array 102 and a backlight module 104. The pixel array 102 and the backlight module 104 are stacked against each other, but they are separately disposed in FIG. 1 to be illustrated more clearly. The pixel array 102 comprises several pixel structures, and the backlight module 104 comprises several parallel cold cathode fluorescent lamps (CCFL) 106.
Generally, a scan-backlight control mode is used to display images for improving the quality of dynamic images. The whole pixel array 102 is divided into several display blocks, that is, display blocks 102a-102d. Similarly, the whole backlight module 104 is also divided into several backlight blocks 104a-104d that correspond to the display blocks 102a-102d positions. Each of the backlight blocks 104a-104d comprises at least one of the CCFLs 106. In the scan-backlight control mode, the display blocks 102a-102d are driven and charged according to a specific sequence. At the same time, the backlight blocks 104a-104d corresponding to the display blocks 102a-102d are also turned on according to the same sequence for displaying a complete image.
Thus, the CCFLs 106 in the backlight module 104 are respectively turned on and off based on blocks of CCFLs 106 rather than being turned on and off at the same time, and the amount of the backlight driver units will increase when the amount of the backlight blocks increases. FIG. 2 shows a driver circuit 200 for cooperating with the backlight module 104 shown in FIG. 1. It can be seen that each backlight block (104a, 104b, 104c, 104d) is driven by one switching circuit (204a, 204b, 204c, 204d) and one transformer (206a, 206b, 206c, 206d). The switching circuits 204a-204d are powered by a DC power supply 202. When one of the backlight blocks needs to be turned on, the switching circuit corresponding to the backlight block should be enabled.
Some problems can be seen from the framework of the driver circuit 200. For example, if there are too many units, such as switching circuits and transformers, in the driver circuit 200, the weight and volume of the flat panel display will be substantially increased, and the circuit will become more complicated. In addition, a great quantity of the switching circuits usually accompanies a great quantity of the switching motions, and the power consumed will be substantial. These problems will become obstacles for the development of LCD displays, and especially for small size LCD displays.